[PATCH] D29454: [DAGCombine] RFC: Recognise any_extend_vector_inreg and truncation style shuffle masks

[Elena Demikhovsky via Phabricator via llvm-commits]

delena added inline comments.


================
Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14268
+  for (unsigned Scale = 2; Scale < NumElts; Scale *= 2) {
+    if ((NumElts % Scale) != 0)
+      continue;
----------------
I don't understand why do you need this check.
You check Mask in IsTruncate(), it should be enough.


================
Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14276
+    // TODO: handle more extension/truncation cases as cases arise.
+    if (EltSizeInBits == ExtSrcSizeInBits)
+      return DAG.getBitcast(VT, N00);
----------------
I'd check at the beginning, before IsTruncate().
if (N00.getValueType().getSizeInBits() != VT.getSizeInBits())
  return SDValue();



Repository:
  rL LLVM

https://reviews.llvm.org/D29454